A few days before Whitehall closed for the Christmas holidays, Sir Jeremy Heywood, the Cabinet Secretary, invited the Civil Service elite to his South London home. As the wine flowed and the permanent secretaries entered the festive spirit, the mood was relaxed.

Sir Bob Kerslake, the head of the Civil Service, challenged Sir Jeremy to a game of pool on a miniature table belonging to one of the Cabinet Secretary’s children. There was even a special mandarins’ quiz, designed to test the mettle of some of Britain’s brightest brains.